Post by jtyotjotjipaefvj on Feb 9, 2018 3:01:10 GMT

Finding exactly how lasing damage works in-game is difficult as there have been no blog posts detailing exactly how they're implemented. I spent some time looking at the disassembled executable and I'm fairly confident I've determined (at least partially) how lasing damage works, and what causes the ablation rate caps observed by many people here. I'll start by describing my understanding of the game's lasing damage mechanics:

1) Figure out affected depth of material. This seems to only depend on the thermal diffusitivity of armor material, and increasing beam power does not increase affected depth. Additionally, transparent materials choose the larger of optical or thermal penetration based on how opaque the material is.

2) Find affected volume and mass of armor. Since our beam is a circular spot, the volume is a cylinder whose radius is the spot radius and height is the affected depth of material.

3) Compute how much of matter we can heat up to melting temperature. Lasers don't actually seem to heat or boil armor material, just heating to melting temperature seems to count as ablated armor. I'm a little less sure of this bit though. Even if we have leftover energy from slagging the affected volume, it will just get ignored completely.

Finally, multiply the affected volume's mass by the slagging percentage we just computed and we get the mass of slagged armor on this simulation tick of the simulation.

The last sentence is what causes the ablation cap that has been observed to happen with higher lasing intensities. Instead of a flat MW/m² number that's been speculated on the forums, it varies from material to material, which also results in a maximum ablation rate for a given material, no matter how much beam power you pump into it. I'll include a table with ablation caps and peak ablation intensities for a bunch of materials below.

For some materials, like Polyethylene and Aramid Fiber, the ablation cap is ridiculously low, making ships using those materials nearly immune to lasing, especially at ranges where sensor inaccuracy comes into play. The ablation rate can also be circumvented by splitting your beam power over more lasers. A 30 MW/m² laser will waste around 90% of its energy to the ablation cap of PE, but 10 3 MW/m² lasers will not.

The current mechanics make designing lasers quite painful since you'll have to carefully balance your beam intensity and number of lasers with the properties of the intended target materials. Without exact knowledge of game mechanics, it also involves lots of testing and results that don't seem to make much sense. Another issue is that it makes high-powered lasers largely useless, since the additional energy just gets wasted on materials that have low thermal diffusitivity.

One solution to this issue that I can think of is implementing a separate damage model for high-intensity beams. Instead of slagging the armor, compute how much matter could be boiled off, without any limitation to depth coming in from thermal diffusivity, as gaseous matter would quickly leave the lased spot due to the high temperatures and pressures involved. This would take a lot more energy per kg of boiled material than melting, but you would not have to rely on the material's thermal conductivity to get any relevant penetration depth out of your beam.

Post by jtyotjotjipaefvj on Feb 9, 2018 3:08:31 GMT

Oh, another note on the damage mechanics. I noticed that the cosine of beam inclination angle is multiplied into the ablation rate after the ablation cap has been applied, instead of multiplying the incoming intensity with the cosine. This means that even aluminum whipple shields can withstand beams with power in the hundred MW/m² range as long as your ship has a pointy enough nose. I'm fairly sure that this at least is a bug.

Post by AdmiralObvious on Feb 9, 2018 3:09:46 GMT

This actually makes a lot of sense, and explains the whole 5 lasers are better than one of the same power totaled up.

I wouldn't go as far as to call it a bug, but instead a limitation on the way the game is programed to handle the situation. Thermal diffusivity should still be important, but i'm not sure how you would be able to simulate gaseous armor, evaporating at the point of the laser.

Post by AtomHeartDragon on Feb 9, 2018 18:01:36 GMT

The same radiation, with the same spectrum, at the same intensity and incidence angle causes the same armour to ablate at wildly different rates depending on how many lasers it is emitted from - sounds like a bug to me.

A possible solution would be to account for effects of all sources of laser irradiation before performing ablation calculations for given tick. I don't know the details of the code and algorithms, but the game might already be doing something roughly similar where accounting for different sources of gravity?

Post by Enderminion on Feb 11, 2018 4:05:40 GMT

Oh, another note on the damage mechanics. I noticed that the cosine of beam inclination angle is multiplied into the ablation rate after the ablation cap has been applied, instead of multiplying the incoming intensity with the cosine. This means that even aluminum whipple shields can withstand beams with power in the hundred MW/m² range as long as your ship has a pointy enough nose. I'm fairly sure that this at least is a bug.

IIRC Al can achive total reflection/internal diffraction/Something Else, that can totally prevent laser damage at high enough angles (IRL) (IDK) (I heard that from someone else) (take it with a grain of salt)

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Post by Rocket Witch on Feb 11, 2018 12:15:51 GMT

jtyotjotjipaefvjLaser ablation cap has been known to be material-specific instead of universal since it was first described. Someone (possibly apophys) made the point once that there's little point in increasing the intensity beyond about 2.4MW/m2 (ablation rates of aramid and rubber) at the desired range and this may have been appropriated as a conventional benchmark.

EnderminionQuoth Ian Mallett (whom is around these forums somewhere) with respect to CDE: "Against an incoming 532nm laser, Aluminum armor has a refractive index of 0.90175. This means that you can actually get total internal reflection. Armor slanted at more than ~64.389 degrees will experience no effect whatsoever from the laser, no matter how powerful!"

The claim of "no effect whatsoever" sounds to me as dubious as they come.

Post by apophys on Feb 11, 2018 16:06:28 GMT

jtyotjotjipaefvjLaser ablation cap has been known to be material-specific instead of universal since it was first described. Someone (possibly apophys) made the point once that there's little point in increasing the intensity beyond about 2.4MW/m2 (ablation rates of aramid and rubber) at the desired range and this may have been appropriated as a conventional benchmark.

EnderminionQuoth Ian Mallett (whom is around these forums somewhere) with respect to CDE: "Against an incoming 532nm laser, Aluminum armor has a refractive index of 0.90175. This means that you can actually get total internal reflection. Armor slanted at more than ~64.389 degrees will experience no effect whatsoever from the laser, no matter how powerful!"

The claim of "no effect whatsoever" sounds to me as dubious as they come.

2. I believe imallett has since retracted that statement, due to a problem that cropped up (imaginary part of the refractive index, apparently very relevant for metals) and a lack of easily-googled information and/or available experts to clarify it. (Also, that would be total external reflection, as used for grazing incidence mirrors; he made a typo there.)

Post by jtyotjotjipaefvj on Feb 11, 2018 17:52:19 GMT

jtyotjotjipaefvjLaser ablation cap has been known to be material-specific instead of universal since it was first described. Someone (possibly apophys) made the point once that there's little point in increasing the intensity beyond about 2.4MW/m2 (ablation rates of aramid and rubber) at the desired range and this may have been appropriated as a conventional benchmark.

It seems a lot of stuff I've researched lately has already been "known". Perhaps there should be some easily found collection of info such as this, for example on the wiki? I've only run into very vague references to the ablation cap and nobody seems to have known anything for certain.

Either way now we know how laser ablation works and have numbers that seem to be reliable for lots of materials, as well as a formula for computing the intensity cap for any given material. That's certainly new information at least.

The code for ablation doesn't seem to have any peaks though. I suspect that's just an artifact of the testing methodology, though I could be wrong.

Post by imallett on Feb 11, 2018 18:35:55 GMT

( Indeed. Unfortunately, the imaginary component of the refractive index (which is nonzero for metals) combines with the real component (which is less than 1) to still produce a sub-1 Fresnel coefficient (instead of the 1 you get for total internal (external, as you please; either is correct) reflection), at least for all materials I've encountered. I struckthrough the erroneous parts of the affected the CoaDE posts and g+ posts where I made this error and added clarifications, but I can't change where I was quoted.

However, it is true that slanted armor still is a helpful, if imperfect, defense. At 90° inclination, the Fresnel coefficient actually is 1, and it can be quite close to that elsewhere. This combines with the cosine loss of the beam spread. So diamond (modeled as a per-wavelength constant IOR of 2.4+0.0i) has at 80° incidence in vacuum a Fresnel transmission coefficient of 0.138892, which can be combined with the cosine loss 0.173648 to get a total transmitted irradiance attenuation of 97.5882%. That's not 100%, so you can still damage it, but you need 1.6 orders of magnitude more beam power. )

Post by Enderminion on Feb 11, 2018 20:52:28 GMT

( Indeed. Unfortunately, the imaginary component of the refractive index (which is nonzero for metals) combines with the real component (which is less than 1) to still produce a sub-1 Fresnel coefficient (instead of the 1 you get for total internal (external, as you please; either is correct) reflection), at least for all materials I've encountered. I struckthrough the erroneous parts of the affected the CoaDE posts and g+ posts where I made this error and added clarifications, but I can't change where I was quoted.

However, it is true that slanted armor still is a helpful, if imperfect, defense. At 90° inclination, the Fresnel coefficient actually is 1, and it can be quite close to that elsewhere. This combines with the cosine loss of the beam spread. So diamond (modeled as a per-wavelength constant IOR of 2.4+0.0i) has at 80° incidence in vacuum a Fresnel transmission coefficient of 0.138892, which can be combined with the cosine loss 0.173648 to get a total transmitted irradiance attenuation of 97.5882%. That's not 100%, so you can still damage it, but you need 1.6 orders of magnitude more beam power. )

And, if the beam can't deliver enough energy to the target/and\or/the target has a thermally conductive backing layer, then the armor should be able to radiate most of the heat away

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Post by OMGitsWTF on Feb 11, 2018 21:20:30 GMT

( Indeed. Unfortunately, the imaginary component of the refractive index (which is nonzero for metals) combines with the real component (which is less than 1) to still produce a sub-1 Fresnel coefficient (instead of the 1 you get for total internal (external, as you please; either is correct) reflection), at least for all materials I've encountered. I struckthrough the erroneous parts of the affected the CoaDE posts and g+ posts where I made this error and added clarifications, but I can't change where I was quoted.

However, it is true that slanted armor still is a helpful, if imperfect, defense. At 90° inclination, the Fresnel coefficient actually is 1, and it can be quite close to that elsewhere. This combines with the cosine loss of the beam spread. So diamond (modeled as a per-wavelength constant IOR of 2.4+0.0i) has at 80° incidence in vacuum a Fresnel transmission coefficient of 0.138892, which can be combined with the cosine loss 0.173648 to get a total transmitted irradiance attenuation of 97.5882%. That's not 100%, so you can still damage it, but you need 1.6 orders of magnitude more beam power. )

Armor is usually not the your target though. You usually try to knock out exposed radiators (if possible), turrets and sensors. Applying a high angle to them is harder to achieve than slanting your armor relative to the incomming beam.

Post by jtyotjotjipaefvj on Feb 14, 2018 12:35:04 GMT

I managed to remove the ablation cap from my game by removing the line that applies the maximum limit to ablated armor. Here's what a 10 GW laser looks like at 250 km range now:

Of course, since armor vaporization is not modeled as far as I can tell, this kind of performance is far better than you'd get in real life with the same beam power. Still though, it looks far nicer than what it does in-game currently, which is pretty much nothing.

Edit: here's instructions on how to do the modification yourself if you want to try it out.

1) Get a hex editor. I used this one (https://www.hhdsoftware.com/free-hex-editor) but anything should do.2) load up CDE.exe in the hex editor from your steam folder3) navigate to offset 0x0025931e4) replace the last 2 words (F2 0F) on that line and first two (5D DD) on the next one with 90 90 90 905) save the file and you're done

What this does is it replaces a single min operation that limits ablated armor mass with four NOP (no operation) instructions. Now you'll get unlimited armor ablation instead of the vanilla version that's limited by heat conduction. It's not realistic but allows real death beams, which is nice.

Post by samchiu2000 on Feb 14, 2018 14:15:26 GMT

I managed to remove the ablation cap from my game by removing the line that applies the maximum limit to ablated armor. Here's what a 10 GW laser looks like at 250 km range now:

Of course, since armor vaporization is not modeled as far as I can tell, this kind of performance is far better than you'd get in real life with the same beam power. Still though, it looks far nicer than what it does in-game currently, which is pretty much nothing.

Edit: here's instructions on how to do the modification yourself if you want to try it out.

1) Get a hex editor. I used this one (https://www.hhdsoftware.com/free-hex-editor) but anything should do.2) load up CDE.exe in the hex editor from your steam folder3) navigate to offset 0x0025931e4) replace the last 2 words (F2 0F) on that line and first two (5D DD) on the next one with 90 90 90 905) save the file and you're done

What this does is it replaces a single min operation that limits ablated armor mass with four NOP (no operation) instructions. Now you'll get unlimited armor ablation instead of the vanilla version that's limited by heat conduction. It's not realistic but allows real death beams, which is nice.

It's over.

It's DOOMSDAY FOR OUR BELOVED GUNS!!!

EDIT: Maybe not actually, yet lasers certainly become much more OP after this modification. And i highly recommend using Enderminion 's Photon Deluge Battleship and a few unlucky gunships to try it out